IAM Reader is not enough: App Configuration data access requires a data-plane role. Assign the identity either the Azure App Configuration Data Reader or Azure App Configuration Data Owner role on the store. (The maintainers also noted that a 500 from the service side was a separate bug they were de…

Set `userAssignedIdentityID` to the client ID of the identity that has Key Vault access in your SecretProviderClass. The reporter confirmed this single change resolved the mount failure. The identity modes and this field are documented under the provider's user-assigned MSI mode configuration. Sourc…